Please add a link to a picture, you don't have the rep to add the picture itself but I will take care of that for you as soon as you post the link. Without a picture or more of a description it will be difficult to get an accurate answer.
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Move more comments link to top♦May 31 '11 at 14:12

3 Answers
3

Without seeing what you're referring to, I'd have to guess that it's the power steering reservoir, although it's possible that it could also be the brake fluid.

The power steering cap should have a dipstick type wand to check the level. Before putting anything in it, check the owners manual to determine what type of fluid it needs - some systems use power steering fluid, while others use something like ATF.

If it's brake fluid, it would probably be a bad thing if it was pinkish - that might indicate that someone had added improper fluids to the brake reservoir. The cap to the brake reservoir will not usually have a dipstick.

Thank you - yes it has a dipstick and so is probably the power steering.
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mgbMay 31 '11 at 15:33

Agreed on it sounded like the power steering reservoir. You share an engine and many parts under the hood with my 84 300ZX and the only tank under the hood with a dipstick is the power steering. See this diagram for a general depiction of it courtesyparts.com/pathfinder-parts-wd21-1987-1995/… if the cap is on top (doesn't overlap the edges) and has two pipes coming off of it then you have a match.
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ManiacZXJun 1 '11 at 23:43

Also it looks like it should be on the passenger side, mounted near the wheel well (same as mine is).
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ManiacZXJun 1 '11 at 23:52

It is likely a power steering reservoir, and it should be labeled as such. You do not put anything in it, unless it is low. If it is low, and you are hearing whine, check for a leak. Some power steering systems use transmission fluid as their fluid, but it is a completely separate system from the transmission.